In a UMTS (Universal Mobile Telecommunications System) network, the specifications of long-term evolution (LTE) have been drafted for the purposes of further increasing high-speed data rates, providing low delay and so on (non-patent literature 1). In LTE, as multiple access schemes, a scheme that is based on OFDMA (Orthogonal Frequency Division Multiple Access) is used in downlink channels (downlink), and a scheme that is based on SC-FDMA (Single-Carrier Frequency Division Multiple Access) is used in uplink channels (uplink).
Also, successor systems of LTE (referred to as, for example, “LTE-advanced” or “LTE enhancement” (hereinafter referred to as “LTE-A”)) have been under study for the purpose of achieving further broadbandization and increased speed beyond LTE. In the LTE-A system, a HetNet (Heterogeneous Network), in which small cells (for example, pico cells, femto cells and so on), each having a local coverage area of a radius of approximately several tens of meters, are formed inside a macro cell having a wide coverage area of a radius of approximately several kilometers, is under study (see, for example, non-patent literature 2). Also, in relationship to the HetNet, a study is in progress to use carriers of different frequency bands between the macro cell and the small cells.